Hitherto, there has been known a so-called mechanical power splitting (split type or two-motor type) hybrid driving unit, to be mounted to a vehicle, in which an engine, a generator (second electric motor) and a driving (assist) electric motor (second electric motor) are connected respectively to three elements of a planetary gear unit, the second electric motor is coupled with an output shaft, output torque of the above-mentioned planetary gear unit is continuously controlled through control of the first electric motor, and torque of the second electric motor is combined with the output torque of the planetary gear to be outputted to the output shaft as necessary.
The hybrid driving unit described above is disclosed, for instance, in Japanese Patent Laid-Open No. Hei.08-183347 as a unit for an FF (front-engine and front-drive) type vehicle and in Japanese Patent Laid-Open No. 2002-225578 as a unit provided with a transmission between an electric motor and an output shaft.
By the way, the position and direction of the hybrid driving unit to be mounted and the shape of the casing member will differ from those of the FF type vehicle in mounting such unit to an FR (front-engine and rear-drive) vehicle.
In case of the FR type vehicle, an internal combustion engine, a hybrid driving unit and a propeller shaft are disposed in line in order from the front side in the longitudinal direction of a body. That is, a crankshaft of the engine, input and output shafts of the hybrid driving unit and the propeller shaft are disposed almost in one and same axial line. In the hybrid driving unit, a first electric motor, a second electric motor, a power splitting planetary gear and a transmission are axially stored within the casing member and a plurality of partial cases divided in the longitudinal direction of the casing member to improve the assembility of those devices need to be jointed.
Meanwhile, taking the production of the hybrid driving unit in series and the mountability thereof to a body into consideration, it is preferable to dispose the two electric motors adequately corresponding to the specification of the vehicle to which the hybrid driving unit is mounted and of the internal combustion engine to which it is combined from the aspect of the cost performance.
However, because the casing member is divided into the plurality of parts in the hybrid driving unit described above, there is a case of causing a misalignment of the axial center of the casing member. Thereby, the accuracy for supporting rotors of the first and second electric motors may drop, possibly causing vibration due to swirling of the axis. Still more, because the first and second electric motors are stored in the different parts of the case, respectively, it is necessary to provide new casing members corresponding to the two electric motors. Accordingly, it has been disadvantageous for producing the above-mentioned hybrid driving unit in series in accommodating the unit to the FR type vehicle.